1. Field of the Invention
The present invention relates to a multi-layer ceramic substrate assembly and a process for manufacturing the same.
2. Description of the Related Art
A multi-layer ceramic substrate assembly provided with pins to enable it to be used as a connector is known. The pins are mounted on pads on a surface of the substrate, the pads for the pins being connected to via-pads electrically connected to via-conductors in the substrate. Additional pads are connected to the pads for pins, for later modifications of the circuit. Such a multi-layer ceramic substrate assembly is illustrated in FIGS. 1-3. In these figures, 1 denotes a ceramic substrate body having via-conductors 2 and interconnecting lines 3, 4 denotes a via upper pad, 5 an upper insulating layer of polyimide, 6 a pin soldered to the via upper pad 4, and 7 a via lower pad. More specifically, the via upper pad 4 comprises a via pad 11, an I/O (in/out) pin pad 12, a modification pad 13, and connecting patterns 14 and 15.
The modification pads 13 are used when the circuit of the substrate is to be changed from the original circuit, by wiring between the modification pads 13 with a discrete wire, and if necessary, disconnecting the I/O pin pad 12 from the via upper pad 4. The wiring to the modification pad 13 is made by soldering a wire to the pad 13. To prevent a flow of a solder from the modification pad 13 to the I/O pin pad 12 during the reflow of the solder, a solder dam 16 is provided between the modification pad 13 and the I/O pad 12, the solder dam 16 being made of a resin such as polyimide (FIG. 3). The solder dam 16 mechanically prevents a flow of the solder 17, but cannot prevent a diffusion of the solder 17 under the resin solder dam 16, i.e., along the surface of the underlying gold plating layer 18, which is a common material used for the pads 11, 12 and 13 as well as the connecting patterns 14 and 15, because the gold plating layer is very easily wetted by the solder. If the solder flows from the modification pad 13 onto the I/O pin pad 12, the solder fixing the I/O pins is damaged and the fixing of the I/O pins is adversely affected, making the connector difficult to use. This adverse affect on the fixing of the pins must be prevented.
The object of the present invention is to provide a solder dam which prevents the flow of a solder between pads.